Process for separating fibrous material

ABSTRACT

Fibrous material such as mineral wool fiber is separated from mixtures of the fibrous material and adhered shot without substantially destroying the fiber length by passing a water suspension of the fibrous material-adhered shot through an attrition device to gently abrade the fiber-shot interface; further diluting the abraded mixture with water; gently agitating the diluted mixture; and decanting to separate the substantially unbroken fibers from the now separated shot.

United States Patent Roberts et a1.

PROCESS FOR SEPARATING FIBROUS MATERIAL Inventors: James R. Roberts, Palatine; Stephen G. Nason, Arlington Heights, both of 111.

United States Gypsum Company, Chicago, 111.

Filed: Dec. 15, 1972 App]. No.: 315,399

Assignee:

US. Cl 241/4, 209/3, 209/162, 241/24 Int. Cl. B02c 19/12 Field of Search 209/2, 3, 162, 163, 173; 65/10; 162/152, 156; 241/4, 14, 24, 28

References Cited UNITED STATES PATENTS 2/1907 Sovereign 241/24 X 5/1929 Rose 209/2 1/1932 Russell 162/227 i451 Feb. 11, 1975 Shaver 162/152 3,354,031 ll/l967 3,765,611 10/1973 Steniger 241/28 X Primary Examiner-R0bert Halper Attorney, Agent, or Firm-Samuel Kurlandsky, Esq.; Stanton T. Hadley, Esq.; Kenneth E. Roberts, Esq.

[57] ABSTRACT 3Claims, 1 Drawing Figure PROCESS FOR SEPARATING FIBROUS MATERIAL BACKGROUND OF THE INVENTION This invention concerns a process for separating fibrous material from adhered unfiberized particles or granules, normally called shot;" and more particularly to a wet process for separating adhered shot from mineral wool without substantial destruction of fiber length.

In many normal manufacturing procedures, fibrous materials are formed by converting a stream of molten raw material into fibers. The manufactured fibrous materials, formed in this way, have a serious disadvantage in that a considerable quantity of unfiberized particles, commonly identified as shot, becomes both loosely intermixed with the fibrous materials and actually adhered to the fibrous material, and are carried into the final product. This disadvantage is particularly onerous with regard to the adhered shot which is difficult to remove without breaking substantial amounts of the fibers into small fragments.

Adhered shot is a problem in both thin products such as mineral fiber paper and thicker products such as bats, felts and boards. In mineral fiber papers, such as those set forth in U.S. Pat. No. 3,562,097, and the like, a smooth surfaced sheet is important and substantial quantities of shot in the sheet would roughen the surface and tend to decrease the directional strength differential of the sheets. In the case of mineral boards and like products excessivevshot content significantly increases the weight of the board thus affecting shipping costs and causing problems in handling. Further it is generally desirable to have a more porous board and shot content adversely affects this property.

In addition, substantial usages exist for the separated shot. For example, clean mineral wool shot is marketable for use in sand blasting operations.

Numerous attempts have been made to remove or reduce the quantity of the unfiberized particles in the fibrous materials, but in general, these attempts have not been greatly successful, particularly with regard to adhered shot. This is particularly true in the mineral wool industry wherein the conventional systems of fiberization for converting the stream of molten raw material into fiber often produce fiber containing very considerable quantities of the shot in the final mineral wool felt. Where the shot is merely loosely mixed with the mineral wool fibers, methods have been developed for separating the loose shot. For example, U.S. Pat. No. 3,142,869 discloses a process and apparatus for a dry air separation of loose shot from mineral fiber and U.S. Pat. No. 2,3 86,975 discloses an apparatus for separating loose shot from mineral wool and the like again using a dry process and an air means for the separation. U.S. Pat. No. 3,354,031 briefly alludes to separating adhered shot from mineral glass fibers by a dry process of shredding and granulating followed by screening; which process would be highly objectionable as substantially decreasing the length of the fiber strands.

A number of other processes have been disclosed for treating fibrous materials to separate them from more dense impurities such as occluded residual foreign particles, like metal, such as disclosed in U.S. Pat. Nos. 2,702,162; 2,711,822; and 281,769.

U.S. Pat. No. 1,841,678 discloses separating granular materials from mineral fiber by upwardly agitating fibers in a liquid and separatingthe fibers from the "pre cipitated" granular material settling out below; which process would appear operable for denser foreign objects as well as probably loose shot, but would not effectuate any separation of adhered shot and mineral wool fibers.

The separation of adhered shot from fibrous materials such as mineral wool is particularly onerous because the shot and the fiber have the same composition and hence the same densities, thus being particularly nonsusceptible to gravitational separation. Further, the adherence of the shot particle to the fiber is very tenacious. The mineral wool fibers especially when in collected form such as in tufts or felts, are generally brittle and delicate; and rough treatment would cause the mineral wool fibers to be broken or destroyed. There is, to our knowledge, no presently known commercial process for readily and easily separating adhered shot from mineral fibers without substantially destroying the fiber length.

SUMMARY OF THE INVENTION It is therefore one object and advantage of the presentinvention to provide a process for separating shot and fibrous materials from mixtures of fiber and adhered shot.

Another object is the provision of a process for separating adhered shot from fibrous masses without substantially breaking or destroying the length of the fibrous material.

Still another object is the provision of an easily operable and economic process for separating adhering shot from masses of fibrous material.

A further object is the provision of such a process applicable to mineral wool.

The fulfillment of these and other objects and advantages of the present invention are accomplished by the steps of passing a dilute aqueous mixture of fibrous material having unfiberized particles adhered thereto through an attrition means to gently abrade the fibershot interface; further diluting the mixture of the abraded shot-fiber mixture with water; gently agitating the water, fiber and shot mixture; and decanting the agitated mixture to separate the substantially unbroken fibers from the now settled shot particles.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a partial sectional elevational view of preferred apparatus for performing the process briefly showing a hydrapulper l; a disc refiner 10, and an agitation vessel 20.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The strands of fiber are broken loose from the adhered shot by gently abrading in an attrition device, preferably a hydropulper shown as l in the drawing or a paper refiner such as the disc refiner I0, and the like. Preferably the fiber 2 adhered shot 3 is first formed into a dilute suspension with water to pass through the attrition device. Generally the water mixture will contain from about 4 to about 10 percent and preferably about 6 percent of shot-fiber by weight. The water suspension of shot-fiber will be passed into the body 4 of the hydropulper l, which may be any common, commercially available and common type used in the paperand pulp refining industry. In this attrition device, op-

posed rotating discs 11 and 12 are contained in housing t 13 having a sealed-feed 14 and discharge 15 means. For

use in the present invention, the distance between the opposed rotating discs 11 and 12 of the disc refiner or the rotor and body 4 of the hydropulper will generally range from about l/l6th inch to about Ainch; with a preferred distance being about /sinch. The distances.

will vary depending upon the feed rate, .with a higher feed rate utilizing a wider spacing than herein set forth and a lower feed rate utilizing a narrower spacing then herein set forth. The aforementioned specific spacings are for a feed rate approximately 5 tons per hour.

Thereafter the deshotted fiber 16 and separated shot 17 are fed to the agitation vessel 20.

In a highly optimized embodiment as set forth in the drawing, two attrition devices such as a hydrapulper l and a disc refiner may be used in series as shown in the dotted lines in the drawing to very gently abrade the shot from the fiber without substantial breakage of the fiber length.

Following the deshotting of the fibers as set forth immediately hereinabove, the water suspension is further diluted to effect separation of the deshotted fiber 16 from the separated shot 17 by glancing effects in agitation vessel 20. Preferably, the water suspension is diluted to a fiber-shot consistency of about A percent to about 2 percent, or in other words, about 9899.75 percent water by weight. A particularly preferred water dilution is about a 1 percent consistency.

The agitation vessel 20 may be any vessel housing 21 equipped with agitation means 22, an inlet means 23, fiber outlet means 24, and shot outlet means 25. Preferably the inlet means 23 for the shot and fiber is located between the fiber outlet 24 and the shot outlet 25; and the shot outlet 25 is located on the bottom or near the bottom of the agitation vessel.

During operation agitation must be continuously supplied to the agitation vessel 20, for if agitation is stopped both the fiber and the shot will settle to the bottom of the tank.

It is preferred to employ the slowest speed of agitation that willcause the fibersto stay in suspension by the natural buoyancy of the fiber due to its elongated shape while allowing the shot to settle due to its generally round shape. A particular speed of agitation or degree of agitation may be determined generally by the configuration of the containing vessel and the type of agitating means used, and thus this figure can vary widely. Generally between 30 and rpm is a suitable value for most available agitators.

With gentle agitation continuing. the now separated fibers are easily decanted by pouring or syphoning off the upper liquid layers, as shown more particularly in the drawing. Further the separated shot is periodically drawn off by syphoning off the very bottom liquid layer.

While the present invention has been described and exemplified with respect to certain embodiments, it is not to be considered limited thereto; and it is understood that variations and modifications thereof, obviousto those skilled in the art, may be made without departing from the spirit or scope of this invention.

What is claimed is:

l. A process for separating mineral wool fibers from adhered mineral wool shot without substantially destroying the mineral wool fibrous character comprising:

passing a suspension of mineral wool fibers having shot particles adhered thereto in water at a solids consistency ofahout 4-l0 percent through an attrition means having attrition plates set at a distance of about l/lo to about A inch apart;

passing said suspension to an agitation vessel and adding water to dilute the mineral wool and shot mixture to a consistency of about /1 percent to about 2 percent by weight;

gently stirring the diluted suspension at a speed of about 30-100 rpm for a time sufficient to free the fibers from the shot; and

continuously decanting, while maintaining agitation,

the fibers and a portion of the water from the shot and the remainder of the water.

2. The process of claim 1 in which the fiber-adhered shot suspension is passed through a disc refiner having the refining plates set at about l/l6 to about A inch apart.

3. The process of claim 2 in which the plates are set at a distance of about A; inch apart. 

1. A PROCESS FOR SEPARATING MINERAL WOOD FIBERS FROM ADHERED MINERAL WOOL SHOT WITHOUT SUBSTANTIALLY DESTROYING THE MINERAL WOOL FIBROUS CHARACTER COMPRISING: PASSING A SUSPENSION OF MATERIAL WOOL FIBERS HAVING SHOT PARTICLES ADHERED THERETO IN WATER AT A SOLIDS CONSISTENCY OF ABOUT 4-10 PERCENT THROUGH AN ATTRITION MEANS HAVING ATTRITION PLATES SET AT A DISTANCE OF ABOUT 1/16 TO ABOUT 1/4 INCH APART; PASSING SAID SUSPENSION TO AN AGITATION VESSEL AND ADDING WATER TO DILUTE THE MINERAL WOOL AND SHOT MIXTURE TO A CONSISTENCY OF ABOUT 1/4 PERCENT TO ABOUT 2 PERCENT BY WEIGHT; GENTLY STIRRING THE DILUTED SUSPENSION AT A SPEED OF ABOUT 30-100 RPM FOR A TIME SUFFICIENT TO FREE THE FIBERS FROM THE SHOT; AND CONTINUOUSLY DECANTING, WHILE MAINTAINING AGITATION, THE FIBERS AND A PORTION OF THE WATER FROM THE SHOT AND THE REMAINDER OF THE WATER.
 2. The process of claim 1 in which the fiber-adhered shot suspension is passed through a disc refiner having the refining plates set at about 1/16 to about 1/4 inch apart.
 3. The process of claim 2 in which the plates are set at a distance of about 1/8 inch apart. 